Multicomponent laminate bodies, particularly soft laminates such as carpets and carpet tiles, are very difficult to monitor or evaluate with respect to quality under dynamic conditions, particularly test conditions involving changes in ambient temperature and moisture, due to the closed nature of such materials.
For example, relatively heavy extrusion backing and the adhesive layers between the backing and the primary carpet facing of a carpet tile usually supply most of the weight, flexibility and structural integrity of the tile. Production and market demands, however, place a severe limitation on the choice of facing/backing combinations, and also limit the number and amount of environmentally-acceptable adhesives which can be used to bind facing and backing layers under high speed production conditions.
Moreover, commercial production of laminates such as carpet tiles usually requires a pre-stretching of primary facing and backing layers to smooth out wrinkles and obtain even surfaces for application of adhesives and mating of the laminate components.
Unfortunately, very few components enjoy the same elastic properties; as a result, adhesive component layers such as hot melt adhesives cannot be set up or cooled precisely enough at high production speeds to assure minimum tension between laminate components and to achieve a consistent adhesive shear strength.
For quality maintenance purposes, the problem is further compounded by the fact that marginally effective adhesive systems (i.e. primary or secondary adhesive layers of carpet tiles) may be adequate to secure and maintain laminate components under one set of test conditions but fail with less ideally matched laminate components tension-wise under identical conditions. In the later situation, art-recognized tests such as the Aachner test.sup.(*1), using statistical analysis of gross external measurements as a criteria over a 100 hour test period, are rarely adequate to evaluate or predict actual or potential quality problems in a meaningful and timely way. FNT .sup.*1 Deutsche Gutegemeinschaft Texteleboden EV. VIN 54318
It is an object of the present invention to develop an accurate method for monitoring the structural integrity of a laminate body.
It is a further object to obtain a sensitive and reliable device for testing and evaluating stress imposed on components within soft laminate bodies such as carpets and carpet tiles.